Diagnose print parsing error on missing report (#454)

When the diagnose command is run and the installation report is missing
the diagnose command crashes with an error.

```
UnhandledPromiseRejectionWarning: TypeError: Cannot read property
  'download_url' of undefined
```

This is because when the report can't be read the
`getInstallationReport` function would only return an empty object,
rather than the expected object with a parsing error. (Expected in the
sense that's how our other integrations handle this type of error and
that's what the diagnose tool on the server side expects.)

With this change the report should no longer crash and the sent report
includes the error about the missing installation report.

I didn't know how to resolve a TypeScript issue with the optional `raw`
key on the parsing error object, so I created a ParsingError type to
indicate that it's a optional key. I couldn't get it to work otherwise.

Part of #448

packages/nodejs/.changesets/report-parse-errors-in-diagnose-report.md

@@ -0,0 +1,5 @@
+---
+bump: "patch"
+---
+
+The diagnose report will report parsing errors on reading or parsing the installation report. Previously, a missing installation report file would crash the diagnose tool.

packages/nodejs/src/cli/diagnose.ts

@@ -32,50 +32,62 @@ export class Diagnose {
     this.print_newline()
 
     console.log(`Extension installation report`)
-    console.log(`  Installation result`)
     const installReport = data["installation"]
-    console.log(`    Status: ${installReport["result"]["status"]}`)
-    const resultMessage = data["installation"]["result"]["message"]
-    if (resultMessage) {
-      console.log(`    Message: ${resultMessage}`)
-    }
-    const resultError = data["installation"]["result"]["error"]
-    if (resultError) {
-      console.log(`    Error: ${resultError}`)
+    const parsingError = installReport["parsing_error"]
+    if (parsingError) {
+      console.log(`  Error found while parsing the report.`)
+      console.log(`  Error: ${parsingError["error"]}`)
+      if (parsingError["raw"]) {
+        console.log(`  Raw report:`)
+        console.log(parsingError["raw"])
+      }
+    } else {
+      console.log(`  Installation result`)
+      console.log(`    Status: ${installReport["result"]["status"]}`)
+      const resultMessage = data["installation"]["result"]["message"]
+      if (resultMessage) {
+        console.log(`    Message: ${resultMessage}`)
+      }
+      const resultError = data["installation"]["result"]["error"]
+      if (resultError) {
+        console.log(`    Error: ${resultError}`)
+      }
+
+      console.log(`  Language details`)
+      console.log(
+        `    Node.js version: ${data["installation"]["language"]["version"]}`
+      )
+      console.log(`  Download details`)
+      console.log(
+        `    Download URL: ${data["installation"]["download"]["download_url"]}`
+      )
+      console.log(
+        `    Checksum: ${data["installation"]["download"]["checksum"]}`
+      )
+      console.log(`  Build details`)
+      console.log(`    Install time: ${data["installation"]["build"]["time"]}`)
+      console.log(
+        `    Architecture: ${data["installation"]["build"]["architecture"]}`
+      )
+      console.log(`    Target: ${data["installation"]["build"]["target"]}`)
+      console.log(
+        `    Musl override: ${data["installation"]["build"]["musl_override"]}`
+      )
+      console.log(
+        `    Linux ARM override: ${data["installation"]["build"]["linux_arm_override"]}`
+      )
+      console.log(
+        `    Library type: ${data["installation"]["build"]["library_type"]}`
+      )
+      console.log(`  Host details`)
+      console.log(`    Root user: ${data["installation"]["host"]["root_user"]}`)
+      console.log(
+        `    Dependencies: ${this.format_value(
+          data["installation"]["host"]["dependencies"]
+        )}`
+      )
     }
 
-    console.log(`  Language details`)
-    console.log(
-      `    Node.js version: ${data["installation"]["language"]["version"]}`
-    )
-    console.log(`  Download details`)
-    console.log(
-      `    Download URL: ${data["installation"]["download"]["download_url"]}`
-    )
-    console.log(`    Checksum: ${data["installation"]["download"]["checksum"]}`)
-    console.log(`  Build details`)
-    console.log(`    Install time: ${data["installation"]["build"]["time"]}`)
-    console.log(
-      `    Architecture: ${data["installation"]["build"]["architecture"]}`
-    )
-    console.log(`    Target: ${data["installation"]["build"]["target"]}`)
-    console.log(
-      `    Musl override: ${data["installation"]["build"]["musl_override"]}`
-    )
-    console.log(
-      `    Linux ARM override: ${data["installation"]["build"]["linux_arm_override"]}`
-    )
-    console.log(
-      `    Library type: ${data["installation"]["build"]["library_type"]}`
-    )
-    console.log(`  Host details`)
-    console.log(`    Root user: ${data["installation"]["host"]["root_user"]}`)
-    console.log(
-      `    Dependencies: ${this.format_value(
-        data["installation"]["host"]["dependencies"]
-      )}`
-    )
-
     this.print_newline()
 
     console.log(`Host information`)

packages/nodejs/src/diagnose.ts

@@ -22,6 +22,12 @@ interface FileMetadata {
   writable?: boolean
 }
 
+interface ParsingError {
+  error: string
+  backtrace: []
+  raw?: string
+}
+
 export class DiagnoseTool {
   #config: Configuration
   #extension: Extension
@@ -84,11 +90,21 @@ export class DiagnoseTool {
   }
 
   private getInstallationReport() {
+    let rawReport
     try {
-      const rawReport = fs.readFileSync(reportPath(), "utf8")
-      return rawReport ? JSON.parse(rawReport) : {}
-    } catch (e) {
-      return {}
+      rawReport = fs.readFileSync(reportPath(), "utf8")
+      return JSON.parse(rawReport)
+    } catch (error) {
+      const report = {
+        parsing_error: {
+          error: `${error.name}: ${error.message}`,
+          backtrace: error.stack.split("\n")
+        } as ParsingError
+      }
+      if (rawReport) {
+        report.parsing_error.raw = rawReport
+      }
+      return report
     }
   }